Peel and chop the onion. Cut the rind from the bacon; cut or chop it into small pieces. Chop the tomato. Heat the oil in a frying pan, add the onion and fry gently for 3-4 minutes, until soft. Add the bacon, and cook for a further 8-10 minutes, stirring well. Add the tomato and seasoning.
Wash the courgettes in cold water and cut a wedge-shaped 'lid' along the length of each courgette, to leave a hollow. Pile the filling into the hollow. Put the courgettes carefully into a greased, ovenproof dish and top with the 'lids'. Cover with a piece of foil and bake in a moderate oven (350F/180C/Gas Mark 4-5) for about 45 minutes. Serve with hot, brown bread rolls and butter, and a green salad.